Slough Fort, Allhallows

Slough Fort (so named due to its proximity to Slough hamlet to the north west) was built between 1861 and 1867 to combat a ever growing threat from the French who were bolstering their coastal defences and naval fleets. One of many stone built forts built along the Kent coastline, the main role of Slough was to prevent the enemy fleet from entering either the River Thames or River Medway; two vitally important channels. The River Thames leading to the Capital, and the River Medway housing Chatham dockyard, the British pride of naval shipbuilding. The initial phase of construction built Slough as a single tower sitting proud on the high ground of The Brimp with seven covered emplacements giving 180 degrees of fire.

Despite being completed in 1867, the first 7-inch RBL (rifles breech loading) guns arrived 4 years later in 1871, but these weapons lacked punch and in 1891 the fort was upgraded to house 9.2-inch and 6-inch able to deter ships out to 10,500 yards. The new weapons enabled Slough to dominate the river approaches to London and were of a revolutionary design, and were housed in a newly designed Twydall profile fort with eastern and western wings. While the previous fort was intended to be a highly visible deterrent to enemy shipping, the new fort of 1891 was hidden behind earthen banks and housed new ‘disappearing guns.’ In conjunction with new smokeless propellants, this steam and hydraulic mechanism enabled the guns to remain hidden below the horizon until firing, when they would raise over the casemate to engage the enemy, fire, and the recoil of firing would facilitate the lowering of the guns and pressurising of the system in preparation for further firings.

Thankfully the fort never saw action against an invading enemy fleet, but continued to be manned during WW1 where the ground defences were strengthened, while the end of the war saw the fort finally disarmed as the capability to protect the Thames fell elsewhere. The last piece of military history in this fort came in WW2 when three anti-aircraft guns were installed on the roof of the old fort, the remains of which remain today.

I visited the fort on Saturday 29 July 2017 during an official open day organised by the Slough Fort Volunteers Group. The fort is still in the ownership of the holiday park, however it is hoped that soon the volunteer trust will take over the management of this monument and continue to uncover more of its history. A potted history from the publication by Victor Smith, August 2016.

Welcome to Slough Fort. The original entrance to the 1867 fort. Note the holes in the steel panel above the door; chains controlling the rise and fall of the draw bridge would have been here.

Exterior, rear wall. This is the outside wall, the flat side of the D, that all visitors would have approached from. This side would have been defensible in the event of a land attack.

A view into six of the original gun positions as constructed in 1867. As the fort changed use, these were repurposed into accommodation for the gun crews. Up to 100 personnel could be accommodated at Slough Fort, but other than training events only a handful of soldiers would have remained.

A view into the old fort, where the distinctive D shape can be seen. The earth and grass level would have been added in the late 19th Century and not during initial construction.

Interior of the old fort. The doorway to the right is the main entrance. The volunteer group have been working to restore original window and doorways as seen by the clean brickwork.

One of the original gun positions in its later configuration as soldier accommodation.

Spiral staircase, of which there is one at either side of the fort.

Second world war anti-aircraft position constructed on top of the old fort.

Second world war anti-aircraft position.

The base of a DRF at Slough Fort dating from WW2 used to accurately plot the course of approaching enemy ships in order for the battery to lay down accurate fire.

A blockhouse and recreation room constructed in 1902, sitting just outside the old fort walls. This building would most likely have had a dual role given the thickness of walls.

The volunteers have been working to clear and restore the gun mountings. This is the left side barbette of the eastern flank.

The left gun position of the eastern flank.

The eastern most barbette as added in the 1891. expansion of the fort.

Stairs down to the eastern magazines. This entire section was filled in during the 1980’s and has only recent been revealed.

Corridors and magazines of the eastern flank.

Magazine and shell lift fittings.

Modern graffiti from the period before the fort was backfilled and buried for three decades.

Corridors and magazines of the eastern flank.

Original painted signs still exist after 120 years, as do the lighting windows. Behind the small window is the lighting corridor, and a single lamp would have sat in this opening, isolated from the magazine area to reduce the risk of accidental fire and ignition of the propellant.

Corridors and magazines of the eastern flank.

Original painted signs still exist after 120 years.

Original painted signs still exist after 120 years, contrasting with modern graffiti from the time before the fort was back filled.

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Frontline Ulster is a website dedicated to tracing the physical remnants of conflict left within Northern Ireland and Ulster through all eras ranging from the early Home Rule crisis through to the cessation of hostilities and the ending of Operation Banner, the longest deployment of the British Army in history. The site aims to focus on the physical archive and archaeological evidence, with less focus placed on the human or political impact. Image copyright is retained by the author unless otherwise stated, and where possible the source has been referenced. Inclusion on this site of any location is not an implied right of access; always attempt to seek landowner permission. No site is safe, always take care and be mindful of any hidden hazards.